Glasspacks and other modifications that increase the noise level of exhaust systems are illegal in the United Kingdom. Some modern muffler designs are similar in principle to the glasspack, but use more sophisticated sound-absorbing materials such as stainless steel mesh, and more advanced acoustical engineering, reducing noise while retaining the power-preserving advantages of a straight-through exhaust flow. This lower flow but slightly quieter design approach is commonly used in glasspack mufflers. 69 Corvette, 3 LT-1 spec with 3' Stahl/ACP headers Thanks, CS. Here's a link if you think it is worth adding to your website. Depending on the directionality of the louvers, one can choose between slightly higher flow capacity or slightly greater muffling. Finally got some good video (more importantly for you, good audio too) of my car running the custom 2.5' x 32 L Cobra Pack mufflers you built for me last year. The more turbulence created, the greater the muffling & less total air flow / power production capacity. The turbulence created by the perforated louvers therefore achieves greater muffling capacity at the expense of total volume of air flow. Other glasspack mufflers have perforated louvers punched into the center core which can reduce total flow capacity. Sound is also dissipated into the fiberglass damping material. A longer glasspack will reduce noise to a greater extent than a shorter one. The distinctive features of the Glasspack mufflers are traditional red powder coating, original straight-through construction and fiberglass inner tube, and its distinctive classic sound.

Since then, the name of Glasspack is closely associated with this brand name, yet today that is not the only company that produces Glasspack mufflers. Glasspack mufflers were originally offered in the United States by Cherry Bomb back in 1968.

Cobra pack mufflers